Method for the manufacture of filaments and fibers from polyethylene oxybenzoate



Dec. 13, 1966 MlKlO KOREMATSU 3,291,778

METHOD FOR THE MANUFACTURE OF FILAMENTS AND FlIjERS FROM POLYETHYLENE OXYBENZOATE Filed Nov. 21, 1963 2 Sheets-Sheet 1 DRAW\NG TEMPERATURE (c) FIG.

Dec. 13, 1966 MlKlO KOREMATSU 3,291,778

METHOD FOR THE MANUFACTURE OF FILAMENTS AND FIBERS FROM POLYETHYLENE OXYBEN'LOATE 2 Sheets-Sheet Filed Nov. 21 1963 TENS\LE STRENTH OF DRAWN FlBER (9/6) ELONGATION AT BREAK OF DRAWN FiBER f QM4L4 M l FIG. 3

United States Patent METHOD FOR THE MANUFACTURE OF FILA- MENTS AND FIBERS FROM POLYETHYL- ENE OXYBENZOATE Mikio Korematsu, Saeki, Japan, assignor to Polyesterether Development Co., Ltd., Tokyo, Japan Filed Nov. 21, 1963, Ser. No. 325,329 22 Claims. (Cl. 260-47) This invention relates to methods for the manufacture of filaments and fibers having excellent quality from polyethylene oxybenzoate.

An object of this invention is to provide methods for the manufacture of filaments and fibers having high thermal shrinkability and also retaining excellent quality even after they are shrunk, being well adapted for use in the manufacture of high bulky textiles.

Another object of this invention is to provide methods for the manufacture of filaments and fibers having high tensile strength, elasticity and thermal stability, being well adapted for use in the manufacture of common textiles.

The polyethylene oxybenzoate used in this invention includes polyesters which are substantially composed of the repeating unit as indicated by the following general formula,

Preferable embodiment of this invention are performed ate tensions are absent.

by using polyethylene oxybenzoate fibers which are proi I duced by the conventional melt spinning method and are substantially neither oriented nor crystallized.

The term unoriented fibers used hereinunder means the fiber having a birefringence (An) of below about 0.05 measured by the conventional method as used D-line of sodium and also the term uncrystallized fibers used hereinunder means the fibers having a degree of crystallization (x) of below 0.15 calculated by the following equation;

wherein d designates the density of polyethylene oxybenzoate fibers measured by the density gradient-tube method as described in the Journal of Polymer Sci., vol. 21, page 44 (1956) by Mr. L. H. Tungetel, K is the constant value of 1384 showing the density of crystalline part of polyethylene oxybenzoate and K is the constant value of 1.312 showing the density of amorphous part of polyethylene oxybenzoate measured by the invent-or as described in the Journal of the Chemical Soc. of Japan, vol. 81, page 852 (1960).

Polyethylene oxybenzoate fibers which are unoriented and uncrystallized can hardly be drawn at a temperature below 70 C. at a practical efficiency but can be drawn at a temperature above 70 C., preferably above 85 C. at a rapid rate.

However, the inventor has found that such fibers could not always be drawn in a stable state and consequently the resulting drawn fibers varied in their properties even when they were drawn to a constant draw ratio at a constant temperature. That is, even if such unoriented and uncrystallized fibers should be drawn to a constant draw ratio at a constant temperature higher than a certain lower limit which varies from 85 to 90 C. depending upon the drawing conditions such as the kind of heating medium, contact time thereto and deformation rate, it is required to drawing them, in onecase, a very low tension and in another case, at very high tension and therefore, there is no intermediate tension to be applied. In addition,

3,291,778 Patented Dec. 13, 1966 duced in fibers under various drawing conditions and the elongation at break of the drawn fibers.

In the accompanying FIGURE 1, the curves 1, 2, 3, 4, 5, 6, 7 and 8 show that the fibers were drawn to the draw ratios of 2.5, 3.0, 3.3, 3.5, 4.0, 4.3, 4.5 and 4.8.

As seen from the curves 1 and 2, when the fibers are drawn to the draw ratio of 2.5 or 3.0 the tension induced in fibers is above 10 kg./mm. at a temperature of about 70 C., decreasing linearly as the temperature rises. In these curves, any abnormal phenomenon is absent.

On the contrary, in the case of curves from 3 to 8, the tension induced in fibers alternates suddenly between high and low values in response to a little above and below the certain temperatures which depend upon the raw ratios, and throughout all these cases the intermedi- For instance, the curve 7 shows a case in which the tension alternates suddenly between about 10 kg./mm. and about 1 leg/mm. in response to a little above and belowthe constant temperature of above C.

When the drawing operation started at 70 C., the initial tension was about 15 kg./rrrm. which decreased gradually as the temperature increased, but as the temperature reached to about 100 C., the tension decreased suddenly from about 8 k-g./mm. to about 0.7 kg./mm.'-

decreasing thereafter very slowly as the temperature in-' creased. On the other hand, when the drawing operation started at C., the initial tens-ion was about 0.5 kg./rnm. which increased very slowly 'as the temperature decreased, but as the temperature reached to about 100 C., the tension increased suddenly from about 0.7 kg./=mm. to 8 kg./mm. increasing thereafter gradually as the temperature decreased. The drawing temperature at which the tension suddenly changed was substantially constant depending upon the draw ratio, if the other operation conditions are constant. The chain curve 9 shown in the accompanying figure was made by plotting the points at which the tension was suddenly changed, and the area on the right hand side enclosed by the chain curve 9 does not include the stable conditions for the drawing operations.

And further, it was observed that the tensile strength and the elongation at break of the fibers which were drawn to the draw ratio of 4.5 at the temperature of 100 C. under the tension of 0 .6 kg./mm. were 2.4 g./d. and 80% respectively, while those of the fibers which were drawn to the same draw ratio but at the temperature of 98 C. under the tension of 9 kg./mm. were 4.3 g./ d. and 31% respectively.

As can be seen from the observation described above, it is obvious that the qualities of the drawn fibers are greatly influenced by the tension induced thereto during the drawing operation, and that even if the fibers are drawn to high draw ratio but under the low tension, no excellent fibers are obtained.

As can be seen from the FIGURES 2 and 3, there exists a. distinct causality between the qualities of drawn fibers and the tension under which they were drawn.

It can be found from the relationship shown in FIG- URES 2 and 3 that it is essentially important to use a tension from above 3 kg./mm. to the extent that no breaking occurs in order to obtain the most useful fibers.

3. This means that the drawing operation must be carried out within the hatched area as shown in FIGURE 1. The hatched area is hereinunder called the available drawing region.

The curves 1 to 8 shown in FIGURE 1 undergo some numerical modification but not in their form depending upon the kind of heating devices or medium such as hot plate, hot water, steam and ultrared ray heater. Consequently, the chain line No. 9 boundarying the available drawing region as shown in FIGURE 1 laid within the range of temperature of from 80 to 120 C. Generally speaking, when the drawing operation is carried out by using a heating medium, for example water, having good thermal conductivity or by taking a long period of time in contact with the heating medium, the boundary line of the available drawing region shifts to a lower temperature. Nevertheless, the causality between the qualities of drawn fibers and the tension under which they were drawn, as shown in FIGURES 2 and 3, is still main tained.

Thus, it has been found by the inventor that the most preferable drawing performance should be done to a draw ratio of above 2.5, at a temperature within the range of 70-120 C. and under a tension of above 3 kg./rnm.

The drawn fibers which are produced by a drawing operation within the available drawing region are subiected to an additional drawing operation to impart them with an overall draw ratio above 3.5 at -a temperature of 90 to 180 C. for improving their qualities.

Table 1 below lists the qualities of fibers drawn under the conditions as follows. The experiment No. 1 was obtained by drawing unoriented and uncrystallized fibers under the condition within the available drawing region, that is, particularly to a draw ratio of 3.8 at the tempera- ;ure of 92 C. under the tension of 4 k-g./mm. The exgeriment No. 2 was obtained by additionally drawing the qreviously drawn fibers of experiment No. 1 to draw ratio at 1.2, that is total draw ratio of 3.8 1.2=4.6, at the temperature of 120 C. The experiment No. 3 was obtained by drawing unoriented and uncrystallized fibers directly to :lraw ratio of 4.6 at the temperature of 120 C. under :he tension of 0.4 kgJrnm. which is outside of the available drawing region.

As can 'be seen from Table 1, the drawing fibers of the experiment No. 2 have the most excellent quality as compared with the drawn fibers of the experiment Nos. 1 and 3.

The rate of crystallization of polyethylene oxybenzoate is not so fast that the degree of crystallization of such drawn fibers is not sufiiciently high. Therefore, they are considerably contracted when heated in a relaxed state and therefore they are undesirable for common textile uses which require to have little thermal contraction at 150 C. An improvement concerning their thermal contraction can be achieved by the heat-treatment at a temperature of 120200 C. under the tension so as to avoid contraction exceeding 5%, to keep them in their length or to stretch them to the extent that no breaking occurs, with the intention of accelerating crystallization while maintaining the molecular orientation. Care must be taken to avoid a contraction of above 5% of their length in this operation because said contraction disturbs their molecular orientation and lowers their Youngs modulus. If the strong and stiff fibers are desired, it is recommended to apply the heat-tr: atment to the drawn fibers at a temperature of 120 to 200 C. under such a tension as that they are allowed to take from a 5% contraction to a 5% stretch at the first stage and then they are allowed to take a stretch from 5% to the extent that no breaking occurs at the second stage.

Table 2 shows the elfect of heat-treatment under a tension applied to the drawn fibers which were obtained by drawing the unoriented and uncrystallized fibers to a draw ratio of 4.4 at a temperature of 95 C. under the tension of 7 kg/mrnF.

The experiment No. 1 indicates the drawn fibers before heat-treatment. The experiment No. 2 indicates the fibers heat-treated under the tension keeping them in their length at the temperature of 170 C. The experiment No. 3 indicated the fibers heat-treated under the tension allowing them a 3% contraction at a temperature of 160 C. The experiment No. 4 indicates the fibers heattreated under the tension allowing them a 20% stretch at the temperature of 160 C. The experiment No. 5 indicates the fibers heat-treated under the tension keeping them in their length at 140 C. and then allowing them a 30% stretch at the temperature of 170 C.

TABLE. 2

Quality of fibers Experiment Nos. Degree of Tensile Elongation Youngs Contraction erystallizastrength at break Modulus at 150 C.

tion (g./d.) (percent) (kg/mm?) (percent) TABLE 1 Quality of drawn fibers Experiment 0S. Tensile strength Elongation at Youngs Modulus (g./d.) break (percent) (kg/mm?) 3. 8 42 485 .II 4. 5 as 630 I": 2.1 93 210 The fibers thus heat-treated under the tension still retain an internal stress of a thermal contraction as shown in the column Contraction at 150 C. in Tab-1e 2.. That said fibers have such a thermal contraction, however, is undesirable for use in certain textile fibers requiring to have no such thermal contraction. But such a thermal contraction can be completely avoided by heat-setting them in a relaxed state allowing a contraction of above 5% or allowing them to change freely in their length at a temperature of to 200 C.

Table 3 below shows the comparative experimental results. The experiment No. 2 indicates the fibers obtained by heat-setting the pre-tre-ated fibers of the experiment No. 2 in Table 2 at a temperature of 170 C. under a relaxed state allowing them an 8% contraction. The experiment No. 4 shows the fibers obtained by heat-setting the pre-treated fi-bers of the experiment No. 4 in Table 2 at a temperature of 150 C. under a relaxed state allowing them a 7% contraction. The experiment No. 5 indicates the fibers obtained by heat-setting the pre-treated fibers of the experiment No. 5 in Table 2 at a temperature of 170 C. under a relaxed state allowing them a free contraction.

6 kg./mm. which is the outside of the available drawing region of this invention. The experiment No. 5 indicates the fibers obtained by drawing to draw ratio of 4.4 at the temperature of 80 C. under the tension of 7 kg./mm.

As seen from Table 4, each of the experiments Nos. 1 to 3 has both sufficiently low value of X and high value of An, and so each of them has a high thermal shrinkability and excellent tensile strength after shrunk. But the experiment No. 4 has too low value of An, so that it has an inferior tensile strength after shrunk, and the experiment No. 5 has too high value of X, so that it has a low thermal shrinkability.

TABLE 3 Quality of fibers Experiment Nos. Degree of Tensile Elongation Youngs Contraction crystallizastrength at break Modulus at 150 0 tion (g./d.) (percent) (kg/mm?) (percent) According to this invention, it is able to produce the TABLE 4 excellent thermally shrinkable polyethylene oxybenzoate fibers, which can be used as a raw material for the prep- Quality embers aration of bulky materials such as yarns, textiles or knitting articles. Hitherto, fi-bers having high thermal shrink- Experiment Contraction Tensil t N s. T sil when heate streng ability were produced from such a polymer as polyvinyl 3O 0 g g X A M1500 0 when heated chloride, other vinyl polymer or 1ts copolymer Wl'llCh (Ml) (percent) M15000 hardly or a little crystallizes. However, when these fibers (ii/d3 were heated, they shrunk intensely but deteriorate their useful Properties it it? iii? .1? 21%. The inventor has found a method to produce poly- 5.2 0.21 0.100 3.8 ethylene oxybenzoate fibers which not only have the high 2:; 8:32 3:??? g thermal shrinkability but also keep their excellent properties after they are shrunk, taking advantage of such a characteristic property of polyethylene oxybenzoate that the rate of crystallization is very low at low temperature below 100 C. but is very high at high temperature above 120 C. In detail, polyethylene oxybenzoate fibers can be highly oriented which being kept essentially uncrystallized by being drawn at as low temperature as possible, for example below 70 C., in the range of the available drawing region, and thus drawn fibers shrink remarkably while keeping their excellent properties when they are heated at the temperature at which polyethylene oxybenzoate molecules crystallize very fast and their orientation is set.

According to the above described facts, when polyethylene oxybenzoate fibers having high thermal shrinkability should be required, the drawing conditions have to be selected preferably as low temperature as possible down to 70 C. and as high tension as possible to make the value of birefringence higher than 0.07 while keeping the degree of crystallization less than 0.25.

Table 4 below lists the comparative experimental results. The raw fibers used in the experiments Nos. 1 to 5 are unorientated and uncrystallized fibers having a birefringence (An) of 0.01 and a degree of crystallization (x) of 0.03.

The experiment No. 1 indicates the drawn fibers obtained by drawing raw fibers to draw ratio of 4.7 at the temperature of 80 C. under the tension of 10 kg./mrn. The experiment No. 2 indicates the fibers obtained by drawing raw fibers to draw ratio of 4.8 at the temperature of 85 C. under the tension of 12 kg./mm.

The experiment No. 3 indicates the fibers obtained by drawing firstly to draw ratio of 3.4 at the temperature of 75 C. under the tension of 7 kg./mm. and then further to draw ratio of 1.2 that is total ratio of 3.4 1.2==4.1 at the temperature of 80 C. The experiment No. 4 indicates the fibers obtained by drawing to draw ratio of 3.4 at the temperature of 80 C. under the tension of 2.9

This invention is illustrated by way of the following examples but it should be understood that this invention is by no means limited thereby or thereto.

Example 1 Melt-spun polyethylene oxybenzoate fibers having a birefringeuce (An) of 0.01 and a degree of crystallization (x) of 0.05 were drawn to a draw ratio of 4.5 in water at the temperature of C. under the tension of 8 kg./mm. and then heat-treated under the tension keeping them in their length for 2 minutes in an air oven at the temperature of 180 C. and finally they were heatset under the relaxed state allowing them an 8% contraction at the temperature of 160 C. for 20 seconds. Theresulting fibers had a tensile strength of 5.0 g./d., an elongation at break of 47%, a Youngs modulus of 480 kg./mm. and a thermal contraction of 0% at 150 C.

Example 2 Melt-spun fibers which are the same as the fibers used in Example 1 were drawn to a draw ratio of 4.4 in water at the temperature of 80 C. under the tension of 7 kg./mm. and then additionally drawn to a draw ratio of. 1.2, that is total draw ratio of 4.4 1.2=5.3 in contact with a hot plate at the temperature of C. The thus produced fibers were heat-treated under such a tension as keeping them in their length for 1 minute in an air oven at the temperature of 180 C. Then, they were heat-set under such a relaxed state as allowing them to change freely' in their length at a temperature of C. for 1 minute. The resulting fibers had a tensile strength of 5.2 g./d., an elongation at break of 38%, a Youngs modulus of 550 kg./mm. and a thermal contraction of 0% at 150 C. V

Example 3 Melt-spun polyethylene oxybenzoate fibers having a birefringence of 0.005 and a degree of crystallization of 0.05 were drawn to a. draw ratio of 4.5 in contact with a hot plate at the temperature of 100 C. under the tension of 11 kg./mm. and then additionally drawn to a draw ratio of 1.4, that is total draw ratio of 4'.5 1.4=6.3, in contact with a hot plate at the temperature of 160 C., followed by heat-treating under such a tension as keeping them in their length for 30 seconds in an air oven at the temperature of 160 C., and finally they were further heat-set under such a relaxed state as allowing them to change freely in their length at the temperature of 160 C. for 1 minute. i

The resulting fibers had a tensile strength of 5.4 g./d., an elongation at break of 22%, a Youngs modulus of 620 kg./mm. and a thermal contraction of at 15 0 C.

Example 4 Melt-spun fibers which are the same as the fibers used in Example 1 were drawn to a draw ratio of 4.0 in contact with a hot plate at the temperature of 90 C. under the tension of 6 kg./mm. and then additionally drawn to a draw ratio of 1.2, that is total draw ratio of by spraying steam at the temperature of 120 C. onto them. The thus drawn fibers were heatatreated under such a tension as stretching them 3% at the temperature of 170 C. for 30 seconds, and finally were heat-set under such a relaxed state as allowing them 10% contraction at the temperature of 170 C. for 30 seconds.

The resulting fibers had a tensile strength of 3.8 g./d., an elongation at break of 42%, a Youngs modulus of 430 kg./mm. and a thermal contraction of 0% at 150 C.

Example 5 Melt-spun polyethylene oxybenzoate fibers having a birefringence of 0.015 and a degree of crystallization of 0.10 were drawn to a draw ratio of 4.8 in hot water at the temperature of 85 C. under the tension of kg./ mmF. Then the drawn fibers were heat-treated under such tension as keeping them in their length for 1 minute in a steam bath at the temperature of 150 C., and finally they were heat-set under such a relaxed state as allowing them to change freely in their length at the temperature of 160 C. for 3 minutes.

The resulting fibers had a tensile strength of 4.7 -g./d., an elongation at break of 40%, a Youngs modulus of 460 kgn/mm. and a thermal contraction of 0% at 150 C.

Example 6 Melt-spun fibers which are the same as the fibers used in Example 1 were drawn to a draw ratio of 4.8 in hot Water at. the temperature of 75 C. under the tension of kg./mm. The resultingv fibers had a birefringence of 0.120, a degree of crystallization of 0.20, a tensile strength of 5.5 g./d. and an elongation at break of 28% And when they were heated in an air oven for 5 minutes, they shrank 28% and their tensile strength and elongation at break changed to 4.0 g./d. and 40%, respectively.

What I claim is:

1. A method for the manufacture of filaments and fibers from polyethylene oxybenzoate, characterized by drawing melt-spun polyethylene oxybenzoate fibers, which are composed of molecules not substantially oriented and crystallized, to a draw ratio of above 2.5 at a temperature of 70 C. to 120 C. under a tension of above 3 kg./rnm.

2. A method for the manufacture of filaments and fibers from polyethylene oxybenzoate, characterized by drawing melt-spun polyethylene oxybenzoate fibers which are composed of molecules not substantially oriented and crystallized, to :a draw ratio of above 2.5 at a temperature of 70 C. to 120 C. under a tension of above 3 kg./

mm. and then heat-treating the resulting drawn fibers at a temperature of C. to 200 C. under a tension allowing them a contraction of less than 5 3. A method for the manufacture of filaments and fibers from polyethylene oxybenzoate, characterized by drawing melt-spun polyethylene oxybenzoate fibers, which are composed of molecules not substantially oriented and crystallized, to a draw ratio of above 2.5 at a temperature of 70 C. to 120 C. under a tension of above 3 kglmm. and then heat-treating the resulting drawn fibers at a temperature of 120 C. to 200 C. under a tension allowing no change in their length.

4. A method for the manufacture of filaments and fibers from polyethylene oxybenzoate, characterized by drawing melt-spun polyethylene oxy'b'enzoate fibers, which are composed of molecules not substantially oriented and crystallized, to a draw ratio of above 2.5 at a temperature of 70 C. to 120 C. undera tension of above 3 kg/mm. and then heat-treating the resulting drawn fibers at a temperature of 120 C. to 200 C. under a tension stretching them to the extent that no breaking occurs.

5. A method for the manufacture of filaments and fibers from polyethylene oxybenzoate, characterized by drawing melt-spun polyethylene oxybenzoate fibers which are composed of molecules not substantially oriented and crystallized, to a draw ratio of above 2.5 at a temperature of 70 C. to 120 C. under a tension of above 3 kglmm. and then heat-treating the resulting drawn fibers at a temperature of 120 C. to 200 C. under a tension allowing them a contraction of less than 5% and then heat-setting the heat-treated drawn fibers at a temperature of 120 C. to 200 C. in a relaxed state allowing them a contraction of above 5%.

6. A method for the manufacture of filaments and fibers from polyethylene oxybenzoate, characterized by drawing melt-spun polyethylene oxybenzoate fibers, which are composed of molecules not substantially oriented and crystallized, to a draw ratio of above 2.5 at a temperature of 70 C. to 120 C. under a tension of above 3 kg./mm. and then heat-treating the resulting drawn fibers at a temperature of 120 C. to 200 C. under a tension allowing no change in their length and then heat setting the heattreated drawn fibers at a temperature of 120 C. to 200 C. in a relaxed state allowing them a contraction of above 5%.

7. A method for the manufacture of filaments and fibers from polyethylene oxybenzoate, characterized by drawing melt-spun polyethylene oxybenzoate fibers, which are composed of molecules not substantially oriented and crystallized, to a draw ratio of above 2.5 at a temperature of 70 C. to 120 C. under a tension of above 3 kg./mrn. and then heat-treating the resulting drawn fibers at a temperature of 120 C. to 200 C. under a tension stretching them to the extent that no breaking occurs and then heatsetting the heat-treated drawn fibers at a temperature of 120 C. to 200 C. in a relaxed state allowing them a contraction of above 5%.

8. A method for the manufacture of filaments and fibers from polyethylene oxybenzoate, characterized by drawing melt-spun polyethylene oxybenzoate fibers which are composed of molecules not substantially oriented and crystallized, to a draw ratio of above 2.5 at a temperature of 70 C. to 120 C. under a tension of above 3 kg./mm. and then heat-treating the resulting drawn fibers at a temperature of 120 C. to 200 C. under tension allowing them a contraction of less than 5% and then heat-setting the heattreated drawn fibers at a temperature of 120 C. to 200 C. in a relaxed state allowing them to change freely in their length.

9. A method for the manufacture of filaments and fibers from polyethylene oxybenzoate, characaterized by drawing melt-spun polyethylene oxybenzoate fibers, which are composed of molecules not substantially oriented and crystallized, to a draw ratio of above 2.5 at a temperature of 70 C. to 120 C. under a tension of above 3 kg/mm.

and then heat-treating the resulting drawn fibers at a temperature of 120 C to 200 C. under a tension allowing no changein their length and then heat-setting the heattreated drawn fibers at a temperature of 120 C. to 200 C. in a relaxed state allowing them to change freely in their length.

10. A method for the manufacture of filaments and fibers from polyethylene oxybenzoate, characterized by drawing melt-spun polyethylene oxybenzoate fibers, which are composed of molecules not substantially oriented and crystallized, to a draw ratio of above 2.5 at a temperature of 70 C. to 120 C. under a tension of above 3 kg./mm. and then heat-treating the resulting drawn fibers at a temperature of 120 C. to 200 C. under a tension stretching them to the extent that no breaking occurs and then heatsetting the heat-treated drawn fibers at a temperature of 120 C. to 200 C. in a relaxed state allowing them to change freely in their length.

11. A method for manufacture of filaments and fibers from polyethylene oxybenzoate, characterized by drawing melt-spun polyethylene oxybenzoate fibers, which are composed of molecules not substantially oriented and crystallized, to a draw ratio of above 2.5 at a temperature of 70 C. to 120 C. under a tension of above 3 kg./mm. and then additionally drawing the resulting drawn fibers to total draw ratio of above 3.5 at a temperature of 90 C. to 180 C.

12. A method for the manufacture of filaments and fibers from polyethylene oxybenzoate, characterized by drawing melt-spun polyethylene oxybenzoate fibers, which are composed of molecules not substantially oriented and crystallized, to a draw ratio of above 2.5 at a temperature of 70 C. to 120 C. under -a tension of above 3 kg./mm. and then additionally drawing the resulting drawn fibers to total draw ratio of above 3.5 at a temperature of 90 C. to 180 C. and then heat-treating the latter drawn fibers at a temperature of 120 C. to 200 C. under a tension allowing them a contraction of less than 5 13. A method for the manufacture of filaments and fibers from polyethylene oxybenzoate, characterized by drawing melt-spun polyethylene oxybenzoate fibers which are composed of molecules not substantially oriented and crystallized, to a draw ratio of above 2.5 at a temperature of 70 C. to 120 C. under a tension of above 3 kg./mm. and then additionally drawing the resulting drawn fibers to total draw ratio of above 3.5 at a temperature of 90 C. to 180 C. and then heat-treating the latter drawn fibers at a temperature of 120 C. to 200 C. under a tension allowing no change in their length.

14. A method for the manufacture of filaments and fibers from polyethylene oxybenzoate, characterized by drawing melt-spun polyethylene oxybenzoate fibers, which are composed of molecules not substantially oriented and crystallized, to a draw ratio of above 2.5 at a temperature of 70 C. to 120 C. under a tension of above 3 kg./mm. and then additionally drawing the resulting drawn fibers to total draw ratio of above 3.5 at a temperature of 90 C. to 180 C. and then heat-treating latter drawn fibers at a temperature of 120 C. to 200 C. under a tension stretching them to the extent that no breaking occurs.

15. A method for the manufacture of filaments and fibers from polyethylene oxybenzoate, characterized by drawing melt-spun polyethylene oxybenzoate fibers, which are composed of molecules not substantially oriented and crystallized, to a draw ratio of above 2.5 at a temperature of 70 C. to 120 C. under a tension of above 3 kg./mm. and then additionally drawing the resulting drawn fibers to total draw ratio of above 3.5 at a temperature of 90 C. to 180 C. and then heat-treating latter drawing fibers at a temperature of 120 C. to 200 C. under a tension allowing them a contraction of less than 5% and then heat-setting the heat-treated drawn fibers at a temperature of 120 C. to 200 C. in a relaxed state allowing them a contraction of above 5%.

16. A method for the manufacture of filaments and fibers from polyethylene oxybenzoate, characterized by drawing melt-spun polyethylene oxybenzoate fibers, which are composed of molecules not substantially oriented and crystallized, to a draw ratio of above 2.5 at a temperature of 70 C. to 120 C. under a tension of above 3 kg./mm. and then additionally drawing the resulting drawn fibers to total draw ratio of above 3.5 at a temperature of C. to 180 C. and then heat-treating the latter drawn fibers at a temperature of C. to 200 C. under a tension allowing no change in their length and then heat-setting the heat-treated drawn fibers at a temperature of 120 C. to 200 C. in a relaxed state allowing them a contraction of above 5%.

17. A method for the manufacture of filaments and fibers from polyethylene oxybenzoate, characterized by drawing melt-spun polyethylene oxybenzoate fibers, which are composed of molecules not substantially oriented and crystallized, to a draw ratio of above 2.5 at a temperature of 70 C. to 120 C. under a tension of above 3 kg./mrn. and then additionally drawing the resulting drawn fibers to total draw ratio of above 3.5 at a temperature of 90 C. to 180 C. and then heat-treating the latter drawn fibers at a temperature of 120 C. to 200 C. under a tension stretching them to the extent that no breaking occurs and then heat-setting the heat-treated drawn fibers at a ternperature of 120 C. to 200 C. in a relaxed state allowing them a contraction of above 5 18. A method for the manufacture of filaments and fibers from polyethylene oxybenzoate, characterized by drawing melt-spun polyethylene oxybenzoate fibers, which are composed of molecules not substantially oriented and crystallized, to a draw ratio of above 2.5 at a temperature of 70 C. to 120 C. under a tension of above 3 kg./mm. and then additionally drawing the resulting drawn fibers to total draw ratio of above 3.5 at a temperature of 90 C.

to 180 C. and then heat-treating the latter drawn fibers at a temperature of 120 C. to 200 C. under a tension allowing them a contraction of less than 5% and then heatsetting the heat-treated drawn fibers at a temperature of 120 C. to 200 C. in a relaxed state allowing them to change freely in their length.

19. A method for the manufacture of filaments and fibers from polyethylene oxybenzoate, characterized by drawing melt-spun polyethylene oxybenzoate fibers, which are composed of molecules not substantially oriented and crystallized, to a draw ratio of above 2.5 at a temperature of 70 C. to 120 C. under a tension of above 3 kg./mm. and then additionally drawing the resulting drawn fibers to total draw ratio of above 3.5 at a temperature of 90 C. to 180 C. and then heat-treating the latter drawn fibers at a temperature of 120 C. to 200 C. under a tension allowing no change in their length and then heat-setting the heat-treated drawn fibers at a temperature of 120 C. to 200 C. in a relaxed state allowing them to change freely in their length.

20. A method for the manufacture of filaments and fibers from polyethylene oxybenzoate, characterized by drawing melt-spun polyethylene oxybenzoate fibers, which are composed of molecules not substantially oriented and crystallized, to a draw ratio of above 2.5 at a temperature of 70 C. to 120 C. under a tension of above 3 kg./mm. and then additionally drawing the resulting drawn fibers to total draw ratio of above 3.5 at a temperature of 90 C. to 180 C. and then heat-treating the latter drawn fibers at a temperature of 120 C. to 200 C. under a tension stretching them to the extent that no breaking occurs and then heat-setting the heat-treated drawn fibers at a temperature of 120 C. to 200 C. in a relaxed state allowing them to change freely in their length.

21. A method for the manufacture of excellent thermally shrinkable filaments and fibers from polyethylene oxybenzoate, characterized by drawing melt-spun polyethylene oxybenzoate fibers, which are composed of molecules not substantially oriented and crystallized, to a draw 1 1 l 2 ratio of above 2.5 at a temperature of 70 C. to 120 C. 7 References Cited by the Examiner Jnder a. tension of above 3 kg./mm. to thereby produce UNITED STATES PATENTS :lrawn fibers having a birefringence value of above 0.07 V and a degree of crystallization of below 0.25. v 25,50,326 6/1944 Van et 22. Polyethylene oxybenzoate filaments and fibers pre- 5 2,471,023 5/1949 cook et a1 260 78'3 pared by the method as claimed in claim 21, characterized in that said filaments and fibers have a high thermal ROBERT WHITE Pnmary Exammer shrinkability of above 15% when they are heated at F, S, WHISENHUNT, Assistant Examiner. 150 C. 

1. A METHOD FOR THE MANUFACTURE OF FILAMENTS AND FIBERS FROM POLYETHYLENE OXYBENZOATE, CHARACTERIZED BY DRAWING MELT-SPUN POLYETHYLENE OXYBENZOATE FIBERS, WHICH ARE COMPOSED OF MOLECULES NOT SUBSTANTIALLY ORIENTED AND CRYSTALLIZED, TO A DRAW RATIO OF ABOVE 2.5 AT A TEMPERATURE OF 70*C. TO 120*C. UNDER A TENSION OF ABOVE 3 KG./MM.2. 